Apparatus for ultrasonic pipet washing

ABSTRACT

An ultrasonic pipet washer for very complete decontamination of laboratory glass pipets, functioning to give an ultrasonic wash and more importantly an ultrasonic rinse; standard acoustic intensities are obtained with transducers on the bottom of the tank and high intensity is obtained by putting additional transducers on the sidewall. Transducers on the sidewall must be inactive when the solution level lowers past it during emptying and this is done with a liquid level switch. Emptying is through a siphon whose inside arm extends to about 1 inch above the bottom which assures that depth of solution remaining in the tank allowing the bottom transducers to remain active.

*Feb. 1, W72

2,958,332 11/1960 Schueler................................ 3,007,478 11/1961 Leonhardtetal......................

[54] APPARATUS FOR ULTRASGNKC PHPET WASHING [72] Inventor: Sherman S. Fishman, 1961 Stockton St. Primary Examiner-Morris wolk Franclscoi Cahf- 'Assistant ExaminerBarry S. Richman Notice: The portion of the term of this patent subsequent to Aug. 1, 1988, has been disclaimed.

ABSTRACT An ultrasonic pipet washer for very complete decontamina- [22] Filed: 0ct.24, 1965 tion of laboratory glass pipets, functioning to give an ul- [211 pp No I trasonic wash and more importantly an ultrasonic rinse; standard acoustic intensities are obtained with transducers on the bottom of the tank and high intensity is obtained by putting additional transducers on the sidewall. Transducers on the sidewall must be inactive when the solution level lowers past it during emptying and this is done with a liquid level switch. Emptying is through a siphon whose inside arm extends to about 1 inch above the bottom which assures that depth of solution remaining in the tank allowing the bottom transducers to remain active.

6 Claims, 5 Drawing Figures References Cited UNITED STATES PAT ENTS 2,933,097 Richheimer.................. ...1 34/l66X .20 DISTH-LED \30 25 '2' TAP WATER PATENTEDFEB 1m: 3.638.566

POWER SUPPLY 51 g. INVENTOR.

APPARATUS FOR ULTRASONIC PIPET WASHING This invention relates to pipet-washing machines, particularly to ultrasonic cleaning of laboratory pipets.

Conventional pipet washers consist of a tall cylinder with a water inlet on the bottom and a siphon which empties the cylinder when the water level has risen to the top of the siphon. The pipets are placed in a basket which is lowered into the cylinder. Water will then rinse the pipets repeatedly as the cylinder empties and fills. In this way cleaning soaps and chemicals will be diluted until the residual quantities are very small.

There remains a problem of even minute residues of contaminating chemicals and soaps. In very sensitive analyses such as enzyme studies, metabolism experiments, radioisotopes, vitamin assays and trace metal contaminants, where sensitivities are high and even small amounts can be detected as an interfering substance in an experiment, it becomes very important to reach cleanliness levels not attainable with repeated water rinses.

An object of this invention is to provide ultrasonic cleaning in combination with repeated ultrasonic rinsing as a technique in the direction of providing laboratory pipets with a minimum of residual contaminating substances.

Other objects and advantages of this invention will become apparent to those skilled in the art from the following description as illustrated in the attached drawing, in which:

FIG. 1 is a partial section FIG. 2 is a plan view and circuit diagram FIG. 3 is a partial cross section through the siphon FIG. 4 is an alternate plan view showing a round tank and one basket FIG. 5 is an alternate plan showing a rectangular tank for multiple baskets.

Referring in detail to the drawing in which like characters are like parts, FIG. 1 illustrates in partial section an ultrasonic tank which is comprised of a tank liner 11 made ofa material which will transmit ultrasound and not be easily damaged by various cleaning chemicals, stainless steel being an acceptable material; a tank cabinet 12, a siphon assembly 20 which serves the purpose of emptying cleaning chemicals from said tank liner 11; attached to the bottom and the sides of tank liner 11 are piezoelectric transducers 15a, 15b, 15c which are energized by means of coaxial power cable 16 (a, b, c) the transdu cers 15 may be located entirely on the bottom or entirely on the side or in combination. A variety of sizes of the tank liner may be selected according to the requirements of the cleaning job to be done; a plastic isolator 13 is fitted onto the upper edge of tank cabinet 12 so as to dampen the vibration of the tank liner 11 and also serve as a watertight seal; fitting inside the tank liner 11 is a basket assembly 17 which has two forms, a straight handle 27a which allows the basket to be immersed without support or alternatively a basket handle with a support or alternatively a basket handle with a support bend 27b; located near the bottom of tank liner 11 is a basket support bracket 14 on which the basket assembly 17 rests when immersed in position for cleaning of its contents; a liquid level control 35 is fitted close to the tank liner wall and serves the purpose of controlling the transducers 15b, 15c according to the liquid level so that the transducers are not operative when the water level is below the position of the transducer; the lower level switch 3517 will shut off the energy to transducer 15b and the upper level switch 356 controls the transducer 15c. The liquid level control 35 is connected to a power supply by means of wires 34, 36, 37; an elbow 20a is located an inch from the top of tank liner 11 and communicates through tank liner 1! and tank cabinet 12 with an outside elbow 20b by means of a nipple 22 and a spacer locknut 21; an inner siphon tube 18 is attached to elbow 20a; and O-ring 23 provides a watertight seal between the elbow 20a and the locknut 21; an outer siphon tube 19 is connected at its top to the outer elbow 20b; at the bottom of the outer siphon tube 19 is attached a hose bibb outlet 31; positioned close to the bottom of said tank liner 11 and suitably attached is a valve assembly 30 which serves as a fluid inlet. The siphon assembly 20 is shown in FIG. 3 in greater detail. It is readily seen that when the fluid level in the tank liner exceeds the level of the siphon assembly the fluid contents will flow in the direction of the siphon assembly and be removed to the outside.

In the operation of the unit above described it is to be noted that an important relationship exists between the rate of flow entering 25 and the rate of flow exiting 26. The inlet flow rate should be about one-third of the outlet flow rate. This is to allow the inner siphon tube to empty the tank and admit air which breaks the siphon flow otherwise the tank will not refill.

In FIG. 2 the liquid level control 35 is seen in its proper relationship to the basket assembly 17; a heater H may optionally be inserted in the tank area for providing higher operating temperatures which certain cleaning chemicals require. The coaxial cable 16 is connected by means ofa coaxial connector 24 to power line 16a which leads to the power supply and energizes transducer 15a which is independent of the liquid level switch. Line 1612 energizes transducer 15b and is controlled by the lower liquid level switch 35b through a line 36 which actuates a solenoid 39; line energizes transducer 15c and is controlled by an upper liquid level switch 350 through a line 37 which actuates a solenoid 38. Line 34 is common to the upper and lower switches. A power supply 33 provides ultrasonic energy to the system.

In FIG. 4 there is an alternate configuration of tank liner 4] which is shown to be cylindrical and the spacial relationship of the basket assembly 47, a transducer 45, the siphon assembly 40 and the valve assembly 50 are properly shown.

In FIG. 5 we see another alternative shape of tank liner Sll which shows multiple basket assemblies 57, 67 and transducers 55, 65, the siphon assembly 60 and the valve assembly 70 in their proper spacial relationship.

The method of operation which can be manual or automatically programmed by means of suitable timers and solenoidactuated valves and mixers follows the sequence of admitting tap water into the interior of the tank liner until a level is reached which is just below the point at which the siphon will operate. Suitable chemicals are now added. The ultrasonic generator is actuated to provide ultrasonic cleaning. After the cleaning period additional water is admitted which raises the level and allows the siphon to empty the tank. When empty the inner siphon tube will then admit air and the siphoning action will stop. Tap water continues to be admitted and the tank will slowly fill. The ultrasonic energy to transducer 15a remains on while transducer 15b goes on only when the lower liquid level switch 35b is actuated and the transducer 15c goes on when the upper liquid level switch 350 is actuated. This cycle of emptying and filling will continue giving an ultrasonic rinse with tap water for a predetermined period of time, after which the tap water is stopped and distilled water is admitted for the final series of ultrasonic rinse cycles. A typical sequence would be 10 minutes ultrasonic cleaning, 10 minutes ultrasonic tap water rinse and 5 minutes ultrasonic distilled water rinse. This method provides a rapid and effective cleaning procedure for items such as laboratory pipets. Further, it provides for the complete removal of the cleaning chemicals which themselves have become contaminants.

This invention is not limited to the specific embodiments disclosed here but is intended to encompass other modifications apparent to those skilled in the art and in keeping within the scope of the following claims.

I claim:

1. An ultrasonic cleaning apparatus composed of a tank open at the top and having a laterally extending flange around the periphery of the open top, a tank cabinet open at the top and conforming in shape to the tank, sized to receive the tank and engage the tank flange when the tank is inserted in the cabinet; a gasket fitted to the junction of the tank flange and the top of the tank cabinet to prevent entry of liquid into the annulus between the tank and tank cabinet; a siphon tube passing through the tank and tank cabinet at a point below the top of the tank, said siphon tube having its inlet adjacent to the bottom of the tank and its outlet outside the tank cabinet at a level below the tank bottom; a liquid inlet tube passing through the tank cabinet at a level near the bottom of the tank, a valve assembly attached to said inlet tube outside the tank cabinet to control the introduction of liquid into the tank, ultrasonic transducers acoustically coupled to the bottom of the tank, a coaxial cable passing through the tank cabinet and attached at its terminal end to said transducers, a basket support bracket attached to the lateral interior surface of the tank near the tank bottom, and a basket assembly sized to permit its introduction into the tank and to receive support from the basket support bracket.

2. The apparatus of claim 1 wherein said tank is square in cross section.

3. The apparatus of claim 1 wherein said tank is round in cross section 4. The apparatus of claim 1 wherein said tank is rectangular in cross section.

5. The apparatus of claim 1 further comprising a timerrnixer connected to said inlet tube valve assembly comprised of a solenoid-operated, timer-activated tap water flow valve and a solenoid-operated, timer-activated distilled water flow valve, a single outlet pipe mixer, said flow valves being connected to the mixer and electrically connected so that the distilled water valve is opened when the tap water valve becomes closed.

6. An ultrasonic cleaning apparatus composed of a tank open at the top and having a laterally extending flange around the periphery of the open top, a tank cabinet open at the top and conforming in shape to the tank, sized to receive the tank and engage the tank flange when the tank is inserted in the cabinet; a gasket filled to the junction of the tank flange and the top of the tank cabinet to prevent entry of liquid into the annulus between the tank and tank cabinet; a siphon tube passing through the tank and tank cabinet at a point below the top of the tank, said siphon tube having its inlet adjacent to the bottom of the tank and its outlet outside the tank cabinet at a level below the tank bottom; a liquid inlet tube passing through the tank cabinet at a level near the bottom of the tank, a valve assembly attached to said inlet tube outside the tank cabinet to control the introduction of liquid into the tank, ultrasonic transducers acoustically coupled to the bottom of the tank and to the exterior lateral surface of the tank, a coaxial cable passing through the tank cabinet and attached at its terminal end to said transducers, a basket support bracket attached to the lateral interior surface of the tank near the tank bottom, a basket assembly sized to permit its introduction into the tank and to receive support from the basket support bracket, a liquid level switch attached to the interior lateral surface of the tank and so positioned that its sensor element is at approximately the same vertical level as the uppermost portion of the laterally placed transducers, and a power supply electrically connected to the coaxial cable and to the liquid level switch. 

1. An ultrasonic cleaning apparatus composed of a tank open at the top and having a laterally extending flange around the periphery of the open top, a tank cabinet open at the top and conforming in shape to the tank, sized to receive the tank and engage the tank flange when the tank is inserted in the cabinet; a gasket fitted to the junction of the tank flange and the top of the tank cabinet to prevent entry of liquid into the annulus between the tank and tank cabinet; a siphon tube passing through the tank and tank cabinet at a point below the top of the tank, said siphon tube having its inlet adjacent to the bottom of the tank and its outlet outside the tank cabinet at a level below the tank bottom; a liquid inlet tube passing through the tank cabinet at a level near the bottom of the tank, a valve assembly attached to said inlet tube outside the tank cabinet to control the introduction of liquid into the tank, ultrasonic transducers acoustically coupled to the bottom of the tank, a coaxial cable passing through the tank cabinet and attached at its terminal end to said transducers, a basket support bracket attached to the lateral interior surface of the tank near the tank bottom, and a basket assembly sized to permit its introduction into the tank and to receive support from the basket support bracket.
 2. The apparatus of claim 1 wherein said tank is square in cross section.
 3. The apparatus of claim 1 wherein said tank is round in cross section.
 4. The apparatus of claim 1 wherein said tank is rectangular in cross section.
 5. The apparatus of claim 1 further comprising a timer-mixer connected to said inlet tube valve assembly comprised of a solenoid-operated, timer-activated tap water flow valve and a solenoid-operated, timer-activated distilled water flow valve, a single outlet pipe mixer, said flow valves being connected to the mixer and electrically connected so that the distilled water valve is opened when the tap water valve becomes closed.
 6. An ultrasonic cleaning apparatus composed of a tank open at the top and having a laterally extending flange around the periphery of the open top, a tank cabinet open at the top and conforming in shape to the tank, sized to receive the tank and engage the tank flange when the tank is inserted in the cabinet; a gasket filled to the junction of the tank flange and the top of the tank cabinet to prevent entry of liquid into the annulus between the tank and tank cabinet; a siphon tube passing through the tank and tank cabinet at a point below the top of the tank, said siphon tube having its inlet adjacent to the bottom of the tank and its outlet outside the tank cabinet at a lEvel below the tank bottom; a liquid inlet tube passing through the tank cabinet at a level near the bottom of the tank, a valve assembly attached to said inlet tube outside the tank cabinet to control the introduction of liquid into the tank, ultrasonic transducers acoustically coupled to the bottom of the tank and to the exterior lateral surface of the tank, a coaxial cable passing through the tank cabinet and attached at its terminal end to said transducers, a basket support bracket attached to the lateral interior surface of the tank near the tank bottom, a basket assembly sized to permit its introduction into the tank and to receive support from the basket support bracket, a liquid level switch attached to the interior lateral surface of the tank and so positioned that its sensor element is at approximately the same vertical level as the uppermost portion of the laterally placed transducers, and a power supply electrically connected to the coaxial cable and to the liquid level switch. 